Stunning photos in that article!Astronuc said:
phyzguy said:
phinds said:
When it was just a numbering classification, it made perfect sense, which is why Hipparchus defined it that way. But later, when quantitative measurements of brightness arrived, we turned it into a quantitative magnitude scale for measuring brightness. After doing that, we really would rather have a brighter object have a larger magnitude. But that would mean re-defining the scale. So today, the faintest objects we can see with our eyes are m=6.0, the faintest objects seen in large telescopes are about m=30.0 and the sun is m=-26.Office_Shredder said:
One picture is rotated in respect to the other.phinds said:
AH HA! I was looking for 90-degree flips/mirrors/whatever. Not very bright this morning. Thanks.Motore said:
About 33degphinds said:
I'm up way too early this morning (long story) and I was only able to think in 90 degree increments.pinball1970 said:
That doesn't seem to make sense, but it's hard to judge without context. Maybe they just discuss how certain parameters are still not very well known, but that should be a symmetric uncertainty.pinball1970 said:
It's only possible if you can find spectroscopic lines or use other spectroscopic features (like the Lyman break). Taken on its own a UV photon redshifted by a factor 15 to 3 micrometers and a visible light photon redshifted by a factor 5 to 3 micrometers are identical.pinball1970 said:
Ok That makes sense thanks. I think I have come across that beforemfb said:
I have a subscription and the article contains the following relevant sentence:pinball1970 said:
This suggests that the problem affected calculations that compared the relative brightness at different wavelengths.
The shift only tells you the recession speed and, although the shift of the (faint) spectral lines can only be measured to a certain accuracy, the distance that's calculated from that red shift depends on the Hubble constant being a constant. Another quantity that can be measured is the brightness of the observed objects and that can be affected by (unknown) quantities of dust etc. Will they actually know the sort of spectral tilt out towards the IR? I imagine that could affect their distance estimation. But someone will sort it out, I'm sure, with the appropriate frigg factor.pinball1970 said:
Would fit to the Lyman break, which is a drop in intensity at a specific wavelength. A miscalibration of the relative brightness shifts the fitted wavelength.Jonathan Scott said:
That statement seems to show some careless publicity of their results. How ever could they be sure about the red shift if they haven't actually measured it? A bit egg on face iyam.pinball1970 said:
I think you mean 400 light years.mfb said: